Pilot change-over valve with position detoction function

Abstract

The present invention provides a pilot type switching valve with position detecting function. A detected part 21 is formed in an end face in a side of a respiratory chamber 9 of a piston 12a, also a recessed part 22 fitting the detected part 21 is formed in a wall surface of the respiratory chamber 9 in a casing 4, and a photo-sensor 25 for projecting / receiving light to the detected part 21 through a through hole 23 is set up in a position facing in the recessed part 22 of the casing 4, to detect an operating position of the piston 12a, that is, an operating position of a spool 6 by reflecting light from the detected part 21.

Description

technical field [0001] The present invention relates to a pilot-operated directional control valve with a position detection function capable of detecting the operating position of a valve member such as a valve core by light. Background technique [0002] A reversing valve using a magnet to detect the switching position of the spool is known, for example, in Japanese Patent Application Laid-Open No. 2-66784 (microfilm of Japanese Patent Application No. Sho 63-144027). In this reversing valve, a magnet is installed on the spool, and a magnetic sensor is installed on the valve body at the same time. The magnetic sensor detects the magnet moving together with the spool, thereby detecting the switching position of the spool. [0003] However, the reversing valve of the prior art described in the above-mentioned known documents is because it uses a magnet as a detected object, and relies on a magnetic sensor to detect the magnetic mode from this magnet, so it is easily affected ...

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Problems solved by technology

[0003] However, the reversing valve of the prior art described in the above-mentioned known documents is because it uses a magnet as a detected object, and relies on a magnetic sensor to detect the magnetic mode from this magnet, so it is easily affected by an external magnetic field. In an environment such as a welding machine or a large motor through which a large current flows, the external magnetic field generated by the current may cause the magnetic sensor to malfunction, making it difficult to maintain a certain detection accuracy, and there are problems in terms of reliability.

[0004] On the other hand, in the above-mentioned known documents, there is also a proposal to use an optical sensor to detect the switching position of the spool. According to this method, it is possible to detect the position of the spool without being affected by an external magnetic field, but here In a document, the specific composition used to realize the method is not shown

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